1. Field of the Invention
The present invention relates to a method of controlling a side support for use with a seat in a vehicle in which a motor is driven to control the operation of the side support according to the operating conditions of the vehicle to thereby prevent an occupant of the seat from losing his or her sitting position and a side support device for use in such method.
2. Description of the Prior Art
When a vehicle goes around a curve, centrifugal force is generated which may push against an occupant of the vehicle seat laterally. Because of this, the occupant loses his or her sitting position, so that the occupant finds it difficult to support a predetermined sitting position as well as feels uncomfortable. Particularly, when the occupant is a driver of the vehicle, if the driver loses his or her sitting position, then the control of the vehicle can be significantly reduced so that the safe driving of the vehicle cannot be achieved.
In view of this, conventionally a side support device has been supplied which can prevent the occupant from losing his or her sitting position to thereby support the sitting position of the occupant and such side support device has been mounted to the driver's seat and the like.
Specifically, the side support device includes a side support which is disposed in a seat back of the vehicle seat in such a manner that it is able to surround the upper body of the occupant from both sides thereof. That is, the side support is arranged such that it can hold the upper body of the occupant firmly from both sides thereof to restrict the movements of the occupant's upper body to thereby support the sitting position of the occupant by force. However, such constant and forcible holding of the occupant's upper body by the side support deprives the occupant of movement of the freedom of the upper body and impairs the comfortable riding feeling of the occupant, so that the occupant gets uncomfortable and tired. To avoid this, according the above-mentioned conventional side support device, the side support is adapted such that it is normally set at an open position where the side support does not push against or hold between the occupant and, only in case of need, it can be moved to a closed position.
As a method of controlling the operation of the side support, a method is widely known which uses lateral acceleration (that is, accelerations in the right and left directions) as a parameter. The lateral acceleration can be detected directly by means of an acceleration sensor (for example, Japanese Laid-open Utility Model Publication No. 60-97633), or can be found from a vehicle speed, a curvature of the curve or the like (for example, Japanese Laid-open Patent Publication No. 61-67638). If the lateral acceleration goes beyond a reference value, then the side support is moved to the closed position. Also, the parameter is not limited to the acceleration, but, for example, in Japanese Laid-open Utility Model Publication No. 60-97634, the vehicle speed and the steering angle of a driving wheel are used as the parameters, and, in Japanese Laid-open Patent Publication No. 60-197436, the curvature of a curve and the vehicle speed are employed as the parameters.
Also, there is known a so-called power type of side support controlling method in which the side support can be moved directly by driving and controlling a motor by means of operation of a switch. In this method, so long as the switch is depressed on, the motor can be driven continuously, whereby an arbitrary closed or open position can be set manually.
As described above, in the above-mentioned well-known side support controlling methods, the disturbance of the sitting position of the occupant occurring when the vehicle goes around a curve is taken into consideration. However, the running conditions of the vehicle that can disturb the sitting position of the occupant and impair the riding comfort of the occupant are not always limited to the above-mentioned curve running condition. For example, when the vehicle runs along bad roads, the occupant suffers from upward and downward accelerations which cause the occupant to lose his or her sitting position and thus impair the riding comfort of the occupant. In an extreme case, the occupant may bite his or her own tongue. Also, the upward acceleration may be so great that the occupant can be thrown up from the seat to collide with the ceiling of the vehicle. In view of this, it is preferable to be able to move the side support to the closed position as the occasion demands when driving on bad roads.
However, the above-mentioned well-known side support controlling methods are incapable of coping with the bad roads driving conditions of the vehicle properly, since they are developed mainly to control the side support in the curve running conditions and thus, as discussed before, the lateral acceleration, the vehicle speed and the wheel steering angle, or the like are used as the parameters.
Also, in the above-mentioned prior art side support controlling methods, after the side support is moved from the open position to the closed position, for example, if the lateral acceleration as the parameter goes below the reference value and then a given period of time elapses, then the side support is moved back to the open position. For this reason, when the curves are repeatedly traversed in the hill or mountain areas, then the side support is opened and closed repetitively with a high frequency, which annoys the occupant. That is, such methods are not preferred from the viewpoints of the safety driving, the mental fatique of the occupant and the like.
Further, in the above-mentioned power type of side support controlling method, during driving, in order to move the side support, the switch must be depressed continuously for a long period of time (up to 8 seconds). Therefore, control of the side support during driving is complicated and provides an obstacle to safe driving, that is, such control cannot be achieved easily.